大掺量高吸附性石粉高强机制砂混凝土收缩开裂抑制试验

针对大掺量高吸附性石粉高强机制砂混凝土早期易发生收缩开裂的问题,开展了掺加膨胀剂、减缩剂、聚乙烯醇(PVA)纤维、高吸水树脂(SAP)混凝土的早期收缩、抗裂和力学试验,并利用核磁共振仪和扫描电子显微镜对混凝土孔结构和微观形貌进行了测试,揭示抑制收缩开裂的机制。试验结果表明:掺入膨胀剂、减缩剂、PVA纤维、预吸水SAP均能有效抑制混凝土早期收缩和开裂,其中掺预吸水SAP降低早期收缩的效果最好,收缩应变可降低93%,PVA纤维抑制早期开裂的作用最明显,总开裂面积可降低68.26%,同时,掺入两者会使混凝土力学性能提高,而掺入膨胀剂和减缩剂会使混凝土力学性能降低。SEM图像表明,SAP能将预吸收的水分释放到混凝土中,促进水泥水化反应,而PVA纤维的掺入改善了混凝土内部孔隙结构,有良好的填充作用和桥接作用。核磁共振试验表明,抑制收缩开裂的机制是通过改善混凝土孔隙结构,增强界面密实度,从而减小早期收缩,进而提高抗裂性能。      

带切口碳纤维复合材料层板损伤的实验研究

本文采用渗透剂增强的X射线照相法分析了含切口复合材料层板的损伤扩展与材料的破坏机理。试验结果表明这种方法是可行的,可以清楚地观察到材料的内部损伤的发生与扩展。材料的破坏是以切口前缘附近损伤区的扩展为特征的,这个损伤区以基体开裂、分层和少量纤维断裂的形式出现。     

原位聚合碳纤维增强聚甲基丙烯酸甲酯基复合材料损伤与修复研究

基于热塑性复合材料易修复的特性,开展了碳纤维增强聚甲基丙烯酸甲酯(PMMA)基复合材料修复技术研究。研究了工艺温度、压力和时间对复合材料力学性能的影响规律。结果表明：在200℃、0.75 MPa压力下保持10 min可以获得优化的复合材料力学性能。引入低速冲击损伤,使用热压修复工艺修复碳纤维增强PMMA基复合材料的损伤。通过X射线断层扫描测试、超声波无损检测技术和断面摄像方法评估了此复合材料的损伤行为和修复效果。结果表明：低速冲击对碳纤维增强PMMA基复合材料的损伤分为低变形量区域的纵向开裂与分层和高变形量区域的纤维断裂与基体失效的混合模式。碳纤维增强PMMA基复合材料损伤试样经过热压修复后,损伤外形恢复良好,损伤区域大小显著减少,内部的开裂和分层等损伤恢复良好,复合材料压缩强度从140 MPa恢复至263 MPa,达到未损伤复合材料压缩性能(307 MPa)的85.7%。     

对中空纤维膜接触器空间结构的分析与探讨

介绍了中空纤维膜接触器在气体分离、净化以及精馏结构填料替代等方面研究的最新进展,并结合笔者所进行的实验工作,从膜接触器中体系的流动方式、壳程挡板、纤维膜组器的填充密度等方面详细探讨了中空纤维膜接触器的空间结构对于过程传质和分离效果的影响.分析结果表明,在气液接触分离过程中,为有效提高膜接触分离过程的传质系数,大多数研究采用了平流中的逆流方式;壳程挡板的增设可以促进过程的分离效果,但其作用并非始终随挡板数量的增加而增强;膜组器填充密度对壳程传质的影响明显,且大多数实验结果表明,过程分离的总传质系数随填充密度的增加而减小.     

聚苯硫醚复合材料高速冲击破坏特征的微观分析

本工作利用霍普金森分离杆(SHPB)方法,对三种连续玻璃纤维和碳纤维增强聚苯硫醚(PPS)复合材料层压板进行了冲击试验,集中讨论了材料的破坏特征,试图为建立更为合理的高应变速率下复合材料横向冲击动态响应模型提供依据。结果显示,采用不同的铺层设计以及不同的纤维增强所得材料的损伤形貌有很大区别,纤维/树脂的界面粘结对微观开裂机理的影响显着。     

高温高压复合密封材料研究及应用

根据填充改性机理,通过正交试验法对影响胶筒的性能指标进行评价分析,确定耐高温高压多元复合材料最优配比为73%聚四氟乙烯树脂+15%纤维类增强填充剂+7%非金属类润滑填充剂+5%金属类耐磨导热填充剂。室内试验和现场试验证明,最优配比组成的胶筒可承受350℃注汽高温和20 MPa注汽压差,满足了稠油热采井过热蒸汽或超临界蒸汽吞吐封堵的工艺需要。     

塑性铰区采用纤维增强混凝土剪力墙的变形性能研究

为了提高高强混凝土剪力墙的抗震性能,在其潜在塑性铰区采用纤维增强混凝土代替高强混凝土,设计了4片剪跨比为2.1的剪力墙试件,进行了拟静力试验。通过改变纤维增强混凝土区高度、轴压比、纵筋数量、箍筋配箍特征值和水平分布筋数量,研究这种剪力墙的抗震性能。结果表明:这种剪力墙试件的抗损伤能力明显改善;纤维增强混凝土区高度对其变形能力有明显影响;开裂荷载和开裂位移显著提高。根据试验结果,分析了这种剪力墙试件的开裂位移、屈服位移和极限位移,给出了考虑剪切、弯曲变形影响的开裂位移、屈服位移和极限位移的计算公式,公式的预测值与试验值吻合较好。     

疲劳氧化环境中3D SiCf/SiC复合材料损伤演变

研究了疲劳氧化环境中3D SiC_f/SiC复合材料损伤演变,并对该环境中SiC_f/SiC复合材料的失效机制进行了分析。结果表明,疲劳氧化环境中3D SiC_f/SiC复合材料的损伤主要为：基体开裂;热解碳界面相脱粘、氧化及取向性排列;纤维断裂、氧化及其结构的改变。这些损伤使氧化性气体通过基体开裂形成的裂纹不断氧化复合材料内部;界面相脱粘和取向性排列使纤维更容易拔出;纤维的氧化、纤维中无定形碳的增多以及SiC晶粒的长大导致纤维强度降低。     

碳纤维增强环氧树脂基复合材料轴管的低速冲击失效机制及剩余压缩性能

采用落锤冲击试验模拟低速冲击过程,对碳纤维增强环氧树脂基复合材料传动轴的轴管在不同能级冲击下的损伤行为以及冲击后的剩余压缩性能进行了研究;通过ABQUAS有限元分析软件和X射线断层扫描技术(CT）相结合的方法观察了复合材料轴管在受到低速冲击时的损伤形式,研究其内部损伤规律。结果表明,复合材料轴管的抗冲击形变能力随着冲击能量的增加先增强后减弱,在冲击能量为10 ~20 J之间出现最大值。CT无损检测结果显示复合材料轴管的失效形式包括分层损伤、树脂开裂和纤维破裂(断裂)。在低能量冲击时,复合材料轴管主要产生分层损伤和树脂的开裂,而纤维断裂损伤只出现在冲击位置,且随着冲击能量的增加纤维断裂现象愈加显著。有限元仿真结果显示复合材料轴管中的碳纤维在拉伸方向的失效明显小于压缩失效,压缩失效沿纤维排布方向扩散,拉伸失效沿轴向和横向呈十字扩散,轴向失效的程度大于横向失效的程度;而树脂的压缩失效沿轴向从冲击位置向横向扩散,扩散形状近似圆形,越靠近圆心失效越明显,拉伸失效范围呈十字,整体失效沿十字边缘扩散。      

纤维增强磷酸铝基复合材料的制备及性能研究

开展了纤维增强磷酸盐结合陶瓷基复合材料的研究,通过选择合适的增强纤维、结合剂及填充剂,采用叠层一热压固化—烧结的复合工艺,制备出隔热承力陶瓷基复合材料.料浆比例为10∶2.14∶3.00和孔径为1.5mm×1.5mm硅氧纤维布制备出的复合材料性能较好.密度对复合材料力学性能有很大影响,采用硅溶胶浸渍提高密度的方法,密度增加10.22％,抗弯强度增加了92.21％.     

无机中空微球的应用

中空微球是内部中空的特殊球形材料,与实心球和非球形材料相比,它具有许多特殊和优异的物理化学性质。本文中简单介绍了无机中空微球的特点和制备方法,对无机中空微球在催化剂、药物载体、树脂改性填料方面的应用做了比较全面的综述。中空微球由于其特殊的中空及介孔结构,作为催化剂时,可以提高催化活性,延长催化反应时间;作为药物载体时,可提高药物存储量,并延长缓释时间;中空微球的低密度、高比表面积使其适合作为填料,用于树脂的改性。     

填料对阻尼隔声材料的水中插入损失的影响

本文研究了空心玻璃微珠、粉煤灰 (煤胞 )、发泡聚合物等填料对阻尼隔声橡胶材料水中插入损失的影响 ,发现橡胶中加入隔声填料可以明显提高水中插入损失。其中玻璃微珠插入损失最大 ,其次是粉煤灰 ,再次为发泡聚合物 ,而前三者等量混合物略差。玻璃微珠用量以 3 0份为宜 ,水中插入损失随用量增加而降低 ,在3kHz、1 0kHz、2 0kHz三个频段 ,用量 3 0份至 5 0份时 ,插入损失降低幅度较大 ,5 0份以后降低幅度变缓 ,其他频率也有类似情况     

Effects of chemical treatments of hybrid fillers on the physical and thermal properties of wood plastic composites

Hybrid filler reinforced composites are considered as a high performance materials, but limited numbers of researches on hybridizations of wood fibers and mineral fillers were reported. Generally, high amount of filler content in composites can lead to the reduction of interfacial adhesion between matrix polymer and fillers, and it limits their applications. In this study, we measured the changes of tensile strength, water absorption, and thermal properties of composites after chemical treatments to wood fibers and mineral fillers. Coupling agent had its own optimum amount for wood fibers and talc to obtain the highest tensile strength. Talc addition showed little effect of the tensile strength with alkali treated wood fibers. Talc addition and silane treatment showed opposite effects on water absorption. Melting enthalpy was decreased by addition of the fillers because of the reduced amount of the crystallizable resin and because of the interference of the fillers for crystallization process.     

丁腈橡胶中空纤维阻尼新材料的制备及性能

针对丁腈橡胶(NBR)黏度过大和相转化时间较长难于纺制中空纤维的问题, 采用先与聚氯乙烯(PVC)共混改性再用干-湿相转化的方法制备出轻质、低耗材的丁腈橡胶中空纤维阻尼新材料, 探讨了NBR与PVC质量比和共混聚合物质量分数对NBR中空纤维阻尼及力学性能的影响。结果表明: 中空纤维结构阻尼性能明显优于对应的平板膜结构; 调整NBR与PVC质量比和共混聚合物质量分数可优化NBR中空纤维的拉伸性能及阻尼性能; 可通过提高NBR与PVC质量比使NBR中空纤维阻尼材料的损耗因子峰值所对应的温度向低温方向偏移。共混聚合物质量分数为25%, NBR与PVC质量比为80∶20时, NBR中空纤维阻尼损耗因子最大, 达到0.78。      

Polymer assisted hydroxyapatite microspheres suitable for biomedical application

Hollow Microspheres of hydroxyapatite-polymer composite can be used as carriers in drug delivery and fillers in tissue engineering. Based on the concept of soft chemistry, a battery of technique is available in the literature to synthesize hollow microspheres, however, an economically viable synthesis route, having good control over the microarchitect and easy to be scaled up, is yet to be developed. Polymer matrix mediated synthesis of inorganic nanoparticles is known to synthesize nanoparticles with controlled morphology and dimensions. It is termed as biomimetic synthesis. Integrating the biomimetic synthesis of nano-particles and spray drying techniques, a novel process of producing hydroxyapatite-polymer composite hollow microspheres is briefly discussed here.     

以聚偏氟乙烯中空纤维微滤膜为模板制备磁性ZSM-5/Ni中空纤维

以聚偏氟乙烯(PVDF)中空纤维微滤膜为模板, 通过化学镀制备Ni/PVDF纤维, 再经原位水热合成得到ZSM-5/Ni/PVDF纤维, 最后经高温焙烧制得ZSM-5/Ni中空纤维. 用SEM、EDX、XRD、BET、VSM和TG等对样品进行了表征. 考察了水热处理次数和温度对ZSM-5沸石在Ni-P镀层上负载的影响, 结果表明: 化学镀能制得Ni/PVDF纤维, 其磁性可控. 在150℃下两次水热处理Ni/PVDF纤维24h可在镀层上得到致密连续的沸石层, 控制水热处理温度可以控制镀层表面沸石层的厚度. 在550℃的空气气氛中焙烧ZSM-5/Ni/PVDF纤维可以得到完整的ZSM-5/Ni中空纤维, 150℃下两次水热处理24h得到的ZSM-5/Ni纤维, 焙烧后其饱和磁化强度由9.3A·m²/kg提高到20.3A·m²/kg, 其比表面积为108m²/g.     

Preparation of a Novel Micro/nano Tubes via Electrospun Fiber as a Template

Poly (para-xylylene) hollow fibers with inner diameters can be prepared via template fibers electrospun from solutions. The PPX is deposited from the vapor phase and the template fiber is selectively removed by heat treatment or solvent extraction. The PPX is partially crystalline and the crystal modification depending on the route is used to extract the template fiber. The thermal stability of the hollow fibers is only slightly reduced relative to the bulk material and the same holds for the UV-stability.     

Induction heating of mastic containing conductive fibers and fillers

The objective of this research is to examine the induction heating of mastic through the addition of electrically conductive fillers and fibers (graphite and steel wool), and to prove that this material can be healed with induction energy. The effect of fibers content, sand–bitumen ratio and the combination of fillers and fibers on the induction heating of mastic was investigated. It was found that there is an optimum content of fibers for each sand–bitumen ratio, above which mastic cannot be heated any more. This optimum seems to coincide with the optimum electrical conductivity of the mixture shown in [1]. It was found that the maximum temperature reached within a certain time period was a function of the sand–bitumen ratio (s–b) and of the volume content of fibers. The mastic could be heated with the addition of a very low volume of conductive fibers. The fastest heating power was obtained with the mix with the maximum electrical conductivity. Gel-Permeation Chromatography (GPC) was also used to show that there is not ageing of bitumen during the heating process.     

Effect of microstructure and physical parameters of hollow glass microsphere on insulation performance

Hollow glass microsphere (HGM) is a special type of inorganic functional powder with wide applications. HGM can be applied in the insulation area as fillers owing to the hollow structure that is not conductive to the transfer of heat. The mechanism of heat transfer in HGM is analyzed and the thermal conductivity is proved to be the main heat transfer. Then a simple model comprised of continuous solid phase and independent gas phase is proposed to study the methods for decreasing the thermal conductivity of the filled system through the methods of reducing the density of HGM or increasing the stacking coefficient of HGM. This work provides actual guidance for the design and controlled preparation of composite materials with hollow glass microspheres as functional filler.     

Preparation and characterizations of antibacterial PET-based hollow fibers containing silver particles

In this work, we have developed a facile differential pressure route to prepare PET-based hollow fibers containing silver particles (Ag/PET hollow fibers). X-ray Diffraction and Scanning Electron Microscopy were used to confirm the existence of silver particles, and the results showed that 0.1-0.5 μm silver particles were incorporated in the inner side-wall of the hollow portion. Inductively Coupled Plasma Atomic Emission Spectrometer was applied to detect the release behavior of silver ions from various Ag/PET hollow fibers. And the results showed that the release behavior of silver ions was depended on time and the length of the fibers, which may be explained by the water uptake property of the Ag/PET hollow fibers.